Movement disorders affect over 5,000,000 people in the United States. The two most common types of movement disorders are essential tremor (ET),which affects over 4,000,000 and Parkinson's Disease (PD), which affects over 500,000 people. Contemporary treatment of these diseases involves high-frequency stimulation through deep brain stimulation (DBS). This form of therapy is offered to patients who have begun to see failure with standard medical therapy and also to patients in which medical therapy is poorly effective. A DBS procedure involves the placement, with millimetric accuracy, of an electrode in the proximity of functional areas referred to as targets. The main difficulty with the procedure is the fact that targets of interest are not or poorly visible in any imaging modality (e.g., MRI or X-ray CT).Hence, the process of implantation of a DBS electrode is an iterative procedure. An approximate target position is determined pre-operatively from the position of adjacent structures that are visible in MR images. With the patient awake, this position is then adjusted intra- operatively, which is a lengthy process. The entire procedure can take 5-6 hours, and requires expertise from a neurosurgeon, an electrophysiologist, and a neurologist. This combined expertise is only available at a limited number of centers, which is one of the reasons why only 3000 procedures are performed annually despite the much larger number of patients who could benefit from it. The goal of this project is to develop a surgical guidance systems that will assist neurosurgeons in identifying targets of interest pre-operatively and in adjusting target position intra-operatively. If successful, the outcome of this project will be a system that will reduce the duration of the procedure, increase its rate of success, and make it feasible at sites that do not have the expertise found at leading research institutions